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O Level Biology: Disease and Immunity MCQs — Biology

30 multiple-choice questions on O Level Biology: Disease and Immunity from Biology, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

1. Vaccinating most of a population helps control a disease because

  1. the pathogen cannot spread easily
  2. everyone gets passive immunity
  3. antibiotics work better
  4. the pathogen mutates

Answer: A) the pathogen cannot spread easily

Explanation: High vaccination coverage stops transmission. O Level Biology · Topic 12 Disease and Immunity · 12.3 Immunity

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2. The mosquito is called a vector because it

  1. causes the disease itself
  2. produces antibodies
  3. kills the pathogen
  4. carries the pathogen from one person to another

Answer: D) carries the pathogen from one person to another

Explanation: Vectors transmit pathogens. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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3. Smoking during pregnancy may cause

  1. lower birth weight
  2. higher birth weight
  3. immunity in the baby
  4. faster growth of the fetus

Answer: A) lower birth weight

Explanation: CO and nicotine reduce fetal growth. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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4. Draining stagnant water helps control malaria because

  1. it kills the adult mosquitoes directly
  2. mosquito larvae develop in water
  3. mosquitoes drink only clean water
  4. Plasmodium lives in soil

Answer: B) mosquito larvae develop in water

Explanation: Removing breeding sites breaks the life cycle. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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5. A transmissible disease is one that

  1. is inherited
  2. is caused by smoking
  3. is caused by poor diet
  4. can be passed from one host to another

Answer: D) can be passed from one host to another

Explanation: The pathogen can spread between hosts. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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6. How can the spread of antibiotic resistance be reduced?

  1. Stop the course early
  2. Use antibiotics only when essential
  3. Use antibiotics for every cold
  4. Give antibiotics to all farm animals daily

Answer: B) Use antibiotics only when essential

Explanation: Less use means less selection for resistance. O Level Biology · Topic 12 Disease and Immunity · 12.2 Antibiotics

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7. Which component of tobacco smoke causes cancer?

  1. Tar
  2. Carbon monoxide
  3. Oxygen
  4. Nicotine

Answer: A) Tar

Explanation: Tar contains carcinogens. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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8. The cholera toxin causes diarrhoea because

  1. it stops peristalsis
  2. it destroys red blood cells
  3. chloride ions are secreted into the gut and water follows by osmosis
  4. it kills the villi

Answer: C) chloride ions are secreted into the gut and water follows by osmosis

Explanation: Ions lower gut water potential; water moves in. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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9. A drug is any substance that

  1. kills viruses only
  2. modifies chemical reactions in the body
  3. is a protein
  4. is made by bacteria

Answer: B) modifies chemical reactions in the body

Explanation: Definition of a drug. O Level Biology · Topic 12 Disease and Immunity · 12.2 Antibiotics

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10. Emphysema is

  1. a deficiency disease
  2. a viral infection
  3. a blocked coronary artery
  4. breakdown of alveolar walls, reducing surface area

Answer: D) breakdown of alveolar walls, reducing surface area

Explanation: Alveoli are damaged in emphysema. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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11. Which is a way HIV is transmitted?

  1. Shaking hands
  2. Mosquito bites
  3. Drinking clean water
  4. Sharing hypodermic needles

Answer: D) Sharing hypodermic needles

Explanation: HIV is passed in blood and body fluids. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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12. A pathogen is

  1. a disease-causing organism
  2. a vaccine
  3. a white blood cell
  4. an antibody

Answer: A) a disease-causing organism

Explanation: Definition of a pathogen. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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13. Passive immunity is short-term because

  1. antibodies are too strong
  2. no memory cells are made
  3. it uses vaccines
  4. it destroys lymphocytes

Answer: B) no memory cells are made

Explanation: Borrowed antibodies break down. O Level Biology · Topic 12 Disease and Immunity · 12.3 Immunity

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14. HIV weakens the immune system by

  1. destroying platelets
  2. destroying red blood cells
  3. destroying lymphocytes
  4. blocking the trachea

Answer: C) destroying lymphocytes

Explanation: Fewer lymphocytes means fewer antibodies. O Level Biology · Topic 12 Disease and Immunity · 12.3 Immunity

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15. HIV is a

  1. bacterium
  2. protoctist
  3. virus
  4. fungus

Answer: C) virus

Explanation: HIV is a viral pathogen. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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16. Alcohol is described as a depressant because it

  1. slows down the nervous system and reaction times
  2. speeds up the heart
  3. kills bacteria
  4. increases self-control

Answer: A) slows down the nervous system and reaction times

Explanation: Alcohol slows reactions. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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17. Vaccination gives long-term immunity because

  1. antibodies last forever
  2. memory cells are produced
  3. the pathogen stays in the body
  4. it gives passive immunity

Answer: B) memory cells are produced

Explanation: Memory cells respond quickly to later infection. O Level Biology · Topic 12 Disease and Immunity · 12.3 Immunity

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18. A vaccine contains

  1. antibiotics
  2. antibodies from another person
  3. white blood cells
  4. weakened pathogens or their antigens

Answer: D) weakened pathogens or their antigens

Explanation: Vaccines stimulate an immune response. O Level Biology · Topic 12 Disease and Immunity · 12.3 Immunity

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19. Which component of tobacco smoke reduces oxygen transport by the blood?

  1. Tar
  2. Water vapour
  3. Carbon monoxide
  4. Nicotine

Answer: C) Carbon monoxide

Explanation: CO binds to haemoglobin. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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20. Malaria is caused by

  1. a fungus
  2. a bacterium
  3. a virus
  4. a protoctist parasite, Plasmodium

Answer: D) a protoctist parasite, Plasmodium

Explanation: Plasmodium is a protoctist. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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21. Antibodies are made by

  1. phagocytes
  2. red blood cells
  3. lymphocytes
  4. platelets

Answer: C) lymphocytes

Explanation: Lymphocytes produce antibodies. O Level Biology · Topic 12 Disease and Immunity · 12.3 Immunity

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22. Cholera is spread mainly by

  1. water contaminated with faeces
  2. coughing and sneezing
  3. touching skin
  4. mosquito bites

Answer: A) water contaminated with faeces

Explanation: Cholera is waterborne. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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23. Why are antibiotics not used to treat flu?

  1. Flu is not an infection
  2. Flu is caused by a bacterium
  3. Flu is caused by a virus
  4. Antibiotics are too strong

Answer: C) Flu is caused by a virus

Explanation: Antibiotics do not affect viruses. O Level Biology · Topic 12 Disease and Immunity · 12.2 Antibiotics

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24. Antibiotics are used to treat infections caused by

  1. bacteria
  2. all pathogens
  3. viruses
  4. fungi only

Answer: A) bacteria

Explanation: Antibiotics kill bacteria. O Level Biology · Topic 12 Disease and Immunity · 12.2 Antibiotics

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25. Which body defence kills pathogens in food?

  1. Skin
  2. Stomach acid
  3. Mucus in the trachea
  4. Nose hairs

Answer: B) Stomach acid

Explanation: Hydrochloric acid kills microbes. O Level Biology · Topic 12 Disease and Immunity · 12.1 Disease

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